Frost dates for 97917Riverside, OR
The average last spring frost in Riverside is June 7 and the average first fall frost is September 6, giving a typical growing season of about 89 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Jun 7
- Average first fall frost
- Sep 6
- Growing season
- 89 days
Safer after Jun 28 (1-in-10 risk)
Possible by Aug 22 (1-in-10 risk)
Last frost typically in 217 days
Frost risk by date
NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.
| Temperature | Last spring: 90% / 50% / 10% chance | First fall: 10% / 50% / 90% chance | Growing season (50%) | Years with at least one |
|---|---|---|---|---|
| Light frost (36°F) | — | — | 57 days | 100% |
| Frost / freeze (32°F) | May 21 · Jun 7 · Jun 28 | Aug 22 · Sep 6 · Sep 22 | 89 days | 100% |
| Hard freeze (28°F) | May 2 · May 20 · Jun 10 | Sep 2 · Sep 19 · Oct 5 | 121 days | 100% |
Planting calendar for Riverside
Planting windows from the University of Maryland Extension calendar, shifted to your average frost dates. Use them as a starting point and adjust for seed packet instructions and local conditions.
| Crop | Task | Window |
|---|---|---|
| Tomatoes | Start seeds indoors | May 7 – Jul 13 |
| Tomatoes | Transplant outdoors | Jun 23 – May 17 |
| Peppers | Start seeds indoors | May 7 – Jun 7 |
| Peppers | Transplant outdoors | Jul 7 – Aug 7 |
| Eggplant | Start seeds indoors | May 24 – Jun 22 |
| Eggplant | Transplant outdoors | Jul 7 – Aug 7 |
| Cucumbers | Sow outdoors | Jul 7 – May 27 |
| Summer squash | Sow outdoors | Jun 23 – Aug 7 |
| Winter squash & pumpkins | Sow outdoors | Jul 7 – Aug 7 |
| Snap beans | Sow outdoors | Jun 23 – Jun 19 |
| Sweet corn | Sow outdoors | Jun 23 – May 17 |
| Watermelon & cantaloupe | Sow outdoors | Jul 7 – Aug 7 |
| Okra | Sow outdoors | Jun 30 – Jul 23 |
| Peas | Sow outdoors (spring) | May 7 – Jun 22 |
| Potatoes | Plant outdoors (spring) | May 7 – Jul 7 |
| Onions | Start seeds indoors (spring) | Mar 26 – Apr 22 |
| Onions | Transplant outdoors (spring) | May 24 – Jun 22 |
| Broccoli | Start seeds indoors (spring) | Apr 19 – May 23 |
| Broccoli | Transplant outdoors (spring) | May 24 – Jun 22 |
| Broccoli | Start seeds indoors (fall) | May 7 – May 17 |
| Broccoli | Transplant outdoors (fall) | Jun 6 – Jun 17 |
| Cabbage | Start seeds indoors (spring) | Apr 9 – May 7 |
| Cabbage | Transplant outdoors (spring) | May 7 – Jun 7 |
| Cabbage | Start seeds indoors (fall) | Apr 27 – May 27 |
| Cabbage | Transplant outdoors (fall) | May 27 – Jun 27 |
| Leaf lettuce | Sow outdoors (spring) | May 7 – Jul 23 |
| Leaf lettuce | Sow outdoors (fall) | May 27 – Jul 13 |
| Spinach | Sow outdoors (spring) | Apr 30 – Jun 13 |
| Spinach | Sow outdoors (fall) | Jun 13 – Jul 18 |
| Radishes | Sow outdoors (spring) | May 7 – Jun 27 |
| Radishes | Sow outdoors (fall) | May 27 – Jul 28 |
| Kale | Sow outdoors (spring) | May 24 – Jun 13 |
| Kale | Sow outdoors (fall) | May 20 – Jun 27 |
| Carrots | Sow outdoors (spring) | Jun 7 – Jul 23 |
| Carrots | Sow outdoors (fall) | Apr 27 – Jun 12 |
| Garlic | Plant outdoors (fall) | Aug 27 – Sep 27 |
Where these dates come from
ZIP code 97917 is matched to the NOAA station Riverside 7 Ssw, OR, 12.1 km away, at 3,380 ft elevation (406 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Riverside 7 Ssw, OR (used) | 3,380 ft | Jun 7 | Sep 6 |
| Drewsey, OR | 3,515 ft | Jun 5 | Sep 5 |
| Westfall, OR | 3,040 ft | May 7 | Oct 3 |
| Malheur Refuge Hq, OR | 4,118 ft | May 29 | Sep 18 |
Frost dates near Riverside
- Crane, OR 97732 · last Jun 11, first Sep 6
- Juntura, OR 97911 · last Jun 5, first Sep 5
- Drewsey, OR 97904 · last Jun 5, first Sep 5
- Harper, OR 97906 · last May 7, first Oct 5
- Westfall, OR 97920 · last May 7, first Oct 3
- Burns, OR 97720 · last Jun 11, first Sep 6
- Diamond, OR 97722 · last May 29, first Sep 18
- Hines, OR 97738 · last Jun 11, first Sep 6
Frequently asked questions
- When is the last frost in Riverside, OR?
- For ZIP code 97917, the average last spring frost (32°F) is June 7, based on NOAA 1991-2020 climate normals for the Riverside 7 Ssw, OR weather station. There is a 1-in-10 chance of a frost after June 28.
- When is the first frost in Riverside, OR?
- The average first fall frost (32°F) is September 6. There is a 1-in-10 chance of frost by August 22, so tender plants are at risk from that point on.
- How long is the growing season in 97917?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 89 days long.
- Are these frost dates a forecast?
- No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.